Medical therapy equipment having a radioactive source



3 1960 s. STEIN 2,951,162

MEDICAL THERAPY EQUIPMENT HAVING A RADIOACTIVE SOURCE Filed Nov. 25, 1955 5 Sheets-Sheet 1 ilI Inventor Attorney Aug. 30, 1960 s. STEIN 2,951,162

MEDICAL THERAPY EQUIPMENT HAVING A RADIOACTIVE SOURCE Filed Nov. 25, 1955 5 Sheets-Sheet 2 2 h J 4f 24 1 A II f1 22 35 i Inventor Q 4 i I Attorney Aug. 30, 1960 s, 5TE|N 2,951,162

MEDICAL THERAPY EQUIPMENT HAVING A RADIOACTIVE SOURCE Filed Nov. 25, 1955 5 Sheets-Sheet 5 l n venlor J Attorney S. STEIN MEDICAL THERAPY EQUIPMENT HAVING A RADIOACTIVE SOURCE Filed Nov. 25, 1955 s Sheets-Sheet 4 Aug. 30, 1960 5 sTElN 2,951,162

MEDICAL THERAPY EQUIPMENT HAVING A RADIOACTIVE SOURCE Filed Nov. 25, 1955 5 Sheets-Sheet 5 Invenlor B I I I d Attorney United States Patent lVIEDICAL THERAPY EQUIPMENT HAVING A RADIOACTIVE SOURCE Stephen Stein, 54 Dunstan Road, London, England Filed Nov. 25, 1955, Ser. No. 549,211 Claims priority, application Great Britain Nov. 26, 1954 4 Claims. (Cl. 250-106) This invention relates to apparatus for utilising the emanations from radioactive sources for medical therapy and research using radioactive matter as a source of radiation and it has for its object the provision of means whereby a source of radioactive matter may be furnished with suflicient shielding to protect persons in close proximity to said source from a harmful intensity of radiation and at the same time to provide for a controlled exposure of the source to be made by remote control in such a way that a beam of radiation of desired shape, size and direction may be utilised at will for medical therapy and research purposes.

To this end the invention consists of an apparatus comprising a container (hereinafter referred to as the head) for a source of radioactive material, said head being formed of a mass of heavy metal for shielding purposes,

and a mechanism for moving the radioactive source from a shielded or enclosed position to. a partially exposed position.

In the accompanying drawings which illustrate this invention:

Figure 1 is a side elevation of the head and ing device;

Figure 2 is a sectional elevation, on line IIII of Figure 3, drawn to an enlarged scale, of part of the interior of the head;

Figure 3 is an end view partly in section on line III--III of Figure 2;

Figure 4 is a similar view to Figure 2, drawn to a reduced scale, illustrating further details;

Figure 5 illustrates a typical installation for static field therapy;

Figures 6 and 7 illustrate parts of the installation shown in Figure 5 drawn to an enlarged scale; and

Figure 8 illustrates the means for removing and replacing the radioactive source from and into the head.

According to one embodiment of this invention the radioactive source 1 is attached to one end'of a bar 2 of heavy metal of a length suflicient to provide the required degree of shielding along its axis. The bar 2 together with the source 1 hereinafter referred to as the source pencil is mounted in a solid cylinder of heavy metal refererd to hereinafter as the drum 3. The source pencil is mounted parallel to the axis of the drum 3 and at some distance from it. In the symmetrical position on the other side of the drum axis is mounted a so-called light pencil 4, which differs from the source pencil in that a beam shapsmall high power lamp 5 with small filaments occupies a position corresponding with that of the radioactive source 1 in the source pencil.

The drum 3 containing both the source and light pencils, is mounted on two bearings 6 and 7 so that said drum may be rotated freely about its axis in a steel shell 8 containing a large mass of shielding metal 9, so that the source 1 is normally enclosed within the mass of shielding metal. The shell 8 and its filling 9 are provided with a conical aperture 10 leading from the inner end of the 2,951,162 Patented Aug. 30, 1960 chamber containing the drum 3 to the outside of the shell 8, the apex of said aperture coinciding with the lamp 5 and, by the rotation of the drum 3 through one half revolution the lamp and source are caused to exchange places and the source 1 is thereby exposed through the conical aperture 10.

Both source and light pencils are secured into the drum 3 by locks 11 and 12, but may be withdrawn from the rear as and when required by the removal of the cover plate 13. In the case of the source pencil this is carried out remotely by means hereinafter described. The light pencil is normally withdrawn manually.

In order that the drum 3 may be rotated during normal operation the outer or rear end thereof is formed as the rotor of an electric motor by the attachment of a ring 14 of conducting material. This ring lies centrally in a pack of motor laminations 15 mounted on the steel shell 8. These laminations together with their association electric windings 16 form the stator of the motor. When energized the drum proceeds to rotate to the extent only of one half revolution when the drum 3 is brought to rest by a bulfer 17 secured on the drum 3 being brought against a mechanical stop 18 secured on the shell 8. The stop 18 is secured on the outer end of screw 19 secured in an element 20 slidably mounted in a double acting pneumatic cylinder 21 the arrangement giving a cushioning eifect and is designed to prevent damage or vibration due to impact when stopping the heavy rotating drum 3. The windings 16 of the motor are so arranged that the energizing current may be left switched on with the motor stalled, so as to maintain the parts in the operative position. During its half revolution the drum moves against the action of a powerful spring 22 which, when the energizing current is switched off automatically returns the drum 3 to its starting position, a second buffer 23 on the drum at this point is brought against the opposite side of the mechanical stop 18. It will thus be understood that the entire assembly is so designed that with the current off and the drum 3 at rest the lamp 5 is exposed through the conical aperture 10 and that with the current on and the drum 3 at rest the source 1 is likewise exposed through said aperture 10.

Provision is made so that it is not possible to expose the source 1 other than by energizing the motor windings after the appropriate procedure hereinafter described has been carried out. It is, however, possible to shield the source manually in emergency by means of a handle 24 attached to the rear of the drum 3 specifically for that purpose. In the event that shielding of the source is thus accomplished, the drum is locked against all further movement by an automatically actuated lock 25.

The mechanism as described above incorporates a number of switches 26, for the operation of signal lamps, interlocks, warning lights and similar devices.

The head is normally mounted as shown in Figure 5 (which illustrates diagrammatically a part of a possible treatment room) in a yoke 27 within which it may rotate. This rotation may be carried out manually by means of suitable gearing or by means of an electric moe tor contained within the yoke structure. The yoke 27 may be supported in a number of ways in order to provide rotation of the head about an axis perpendicular to that within the yoke and linear translational motion in up to three mutually perpendicular directions. A typical form of mounting as shown in Figure 5 would consist of a horizontal telescopic arm 28 rotatably mounted in a part 29 supported in a part 30 so that it may be raised and lowered in the vertical direction.

Motorised movements of the mounting for the head are conveniently controlled from a mobile pedestal, hereinafter described, hanging pendant or the like. A par- 3 tic'ular feature of the head mounting is the provision within said mounting of adjustable limiting stops or switches for each available movement. The purpose of such devices is to enable the gamma ray beam emerging from the head through the aperture it) when in use to be restricted within a defined range of solid angle and the source to be contained in a defined volume in space.

The mobile pedestal 31 above referred to provided.

with a table 32 as illustrated in Figure 7 may be provided with indicator lamps 33, a plurality of switches 36 for controlling the movements of the head mounting, the power to which is controlled by a foot pedal 37.

In order to use the head for any purpose a remote con trol station is provided in the form either of a panel or desk 38 located outside the treatment room as shown in Figure 5. Exposure of the source may oniy be actuated from this station. This is accomplished by energizing the drum motor windings 16 as indicated heretofore. Before it is possible to expose the source a stipulated number of standard electrical relays or contacts have to be closed. The number of such devices will vary according to requirements but a minimum sequence is provided as follows:

A switch incorporated in a latch to the treatment room door 39 or other suitable barrier.

An interlock to prevent exposure unless the appropriate timing mechanism is set.

Once the required sequence of relays and contacts has been closed the source is exposed by means of a push button switch 49 at the remote control station 38. Once the source It in its rotation has reached a predetermined point near to its fully exposed position, the exposure timing mechanism 41, which has been previously set for the required period, is energized. At the end of this period, the timing mechanism 41 acts to switch off the current to the stalled motor and the source 1 is returned to its shielded position by the spring 22. An exposure recording mechanism 42 may also be provided in order to check the time during which the source 1 was actually exposed. A further indication of the end of an exposure is provided by an audible signal (not shown) switched on by the closing of the timing mechanism and remaining on until the source 1 is returned to its shielded position.

At any time during an exposure the source 1 may be returned to its shielded position by a push button switch 43 at the control station 33. A further safeguard is provided by a main relay 44 which may be used to cut ofi all power to the mechanism. In the event of the spring mechanism 22. failing to return the source 1, a switch 45 is provided for reversal of the motor current in order to drive the source back to its shielded position. As a final emergency procedure a manual return of the source by means of the handle 24 is provided as described previously.

Provision is made so that, if desired, it is not possible to expose the source from the remote control station 38 while power is switched on to the mounting control gear e.g. during the setting up of a patient for treatment. This may be accomplished by a system of key interlocks so that one individual only can operate either the mounting controls on pedestal 31 or exposure controls at remote control station 38.

A visible sign of the position of the source 1 is pro vided by a system of three coloured lamps 33 situated wherever suitable (e.g. treatment room door 39 or mounting control pedestal 31 or remote control station 33) and showing that the source is shielded, moving or exposed. The audible warning is provided whenever the source is exposed or moving and the timing mechanism 4-1 is switched off.

A further safety device intended for service whenever the apparatus is being used to treat a live subject may be provided. This safety device may consist of a pres sure switch or relay arranged in such a way that it is actuated by movement of the subject under treatment. When the safety device is actuated the source is automatically returned to the shielded position.

Provision is made for the attachment to the head of a variety of standard accessories such as fixed applicators, variable diaphragms and penumbra trimmers for beam shaping.

The head may be provided with the usual back and front pointers, pin and are, and optical or mechanical source to skin scales, to assist in the setting up of patients for treatment.

An irradiation chamber may be clipped into the conical aperture 10 of the head, using the multiple shielding block 46 as shown in Figure 4 so that controlled irradiations of living or inanimate matter positioned on the blocks 46x may be carried out without unnecessary exposure of an operator.

In order to exchange the radioactive source for another, the cover plate 13 is first removed and a shielding plug 48 is withdrawn. A transport container is then aligned with the rear end of the drum mechanism and a cable connection 47 from the transport container (not illustrated) is secured at 49 to the source pencil 1 as shown in Figure 8. A thick walled cylinder which may normally form part of the shielding of the transport container is moved to surround the gap between the head and container and the source pencil 1 is withdrawn through the tube 50 into the transport container by remote control. A new source pencil may in like manner be loaded into the drum.

What I claim is:

1. A radiation beam forming unit comprising a mass of metal adapted to form a main shield for a radioactive source, a secondary shielding member in the form of a solid cylinder mounted in a chamber formed in said main shield so as to be capable of rotary movement about the longitudinal axis thereof, the inner end of said chamber being disposed near the centre of the main Shield and there communicating with a beam defining aperture formed in the main shield, said cylinder having formed therein two bores extending longitudinally thereof and disposed in spaced parallel relationship with and on opposite sides of the axis of rotation of the cylinder, a shielding carrier for a radioactive source rem'ovably mounted in one of said bores, a radioactive source receiving element formed at the inner end of said carrier and exposed through the inner end of the respective bore, a light transmitting element mounted in the other of said bores and exposed through the inner end thereof, and means adapted to rotate said cylinder for selectively moving said source receiving element and light transmitting element between an exposure position coincident with the inner end of said beam defining aperture and a safety position remote therefrom in which a radioactive source will be shielded jointly by said rnain shield and the cylinder.

2. A radiation beam forming unit comprising a mass of metal adapted to form a main shield for a radioactive source, a secondary shielding member in the form of a solid cylinder mounted in a chamber formed in said main shield so as to be capable of a rotary movement about the longitudinal axis thereof, the inner end of said chamber being disposed near the centre of the main shield and there communicating with a beam defining aperture formed in the main shield, said cylinder having formed therein two bores extending longitudinally thereof and disposed in spaced parallel relationship with and on opposite sides of the axis of rotation of the cylinder, a shielding carrier for a radioactive source removably mounted in one of said bores, a radioactive source receiving element formed at the inner end of said carrier and exposed through the inner end of the respective bore, a light transmitting element mounted in the other of said bores and exposed through the inner end thereof,

spring means adapted to rotate said cylinder when the unit is non-operative to hold said light transmitting element coincident with said beam defining aperture and said source receiving element in a safety position remote from said aperture in which a radioactive source will be shielded jointly by the main shield and the cylinder, and means operative to rotate said cylinder against the force of said spring means to reverse the positions of the light transmitting element and the source receiving element, said spring means being adapted to return these elements to their initial positions again when said cylinder rotating means become non-operative.

3. A radiation beam forming unit as claimed in claim 2 wherein said cylinder rotating means comprises a motor of which a member connected to the cylinder forms a moving part and co-operating stop means are provided on said cylinder and on a part fixed with respect to the main shield for limiting the movements of the cylinder so as to correctly position the source receiving and light transmitting elements.

4. A radiation beam forming unit as claimed in claim 3 having means for manually rotating said cylinder in the event that said spring means should fail to function when the cylinder rotating means become non-opertative.

References Cited in the file of this patent UNITED STATES PATENTS 1,228,865 Zueblin June 5, 1917 2,477,648 Piggott et a1. Aug. 2, 1949 2,582,776 Greanberg et al. Ian. 15, 1952 2,670,443 Pennock et al. Feb. 23, 1954 2,684,447 Gilks July 20, 1954 2,737,596 Houpt et a1. Mar. 6, 1956 OTHER REFERENCES Brucer: Special Report of the Medical Division on T eletherapy Design Problems, I, Cs137 TID 5086 (211d 2 Rev.), pages 59 to 61, May 15, 1955, 

